Many potentially life-threatening liver diseases affect a significant portion of the human population. One such example is hepatitis B, a liver infection caused by the hepatitis B virus (HBV). It is a major global health problem and the most serious type of viral hepatitis, due to its potential of causing chronic liver diseases, which may ultimately lead to cirrhosis of the liver and liver cancer. Worldwide, an estimated two billion people have been infected with the HBV, and more than 350 million have chronic liver infections though many are asymptomatic. Hepatitis B is endemic in China and other parts of Asia. Most people in those regions become infected with HBV during childhood, and 8% to 10% of the adult population are chronically infected. Liver cancer caused by HBV is among the first three causes of death from cancer in men, and a major cause of cancer in women.
A number of liver function tests have been developed and routinely used in clinics. For example, a patient's blood sample may be tested for the level of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), total bilirubin (TBIL), direct bilirubin, or gamma glutamyl transpeptidase (GGT) for the purpose of assessing liver function. However, because of the high prevalence of liver diseases and the vital importance of early detection and treatment, especially in view of the fact that most liver diseases show only mild symptoms initially, there exists a need for new and more sensitive methods that would allow early diagnosis of liver diseases. This invention fulfills this and other related needs.